Process for chain-extending unsaturated terminated polyimides and products prepared therefrom

ABSTRACT

Aromatic polyimides with reactive end groups are cured by coupling together by addition or condensation to increase molecular weight with little or no by-product formation. These polyimides can be shaped and formed prior to the coupling. The aromatic polyimides appropriate for coupling are formed by the reaction of an aromatic dianhydride and an aromatic diamine in ratios to provide the appropriate end groups, or by including in the reaction mixture a compound which will provide reactive end groups, e.g., aromatic nitrile, allyl, propargyl, styryl, etc. Depending on the reactive end groups present, coupling of the polyimide is carried out either by self-coupling or by reacting the polyimide with a complementary organic compound. Included in the latter is the reaction with an aromatic bisdipole compound which will propagate the polymer chain.

14 1 July 29,1975

PROCESS FOR CHAIN-EXTENDING UNSATURATED TERMINATED POLYIMIDES AND PRODUCTS PREPARED THEREF ROM Gaetano Francis DAlelio, South Bend, 1nd.

University of Notre Dame du Lac, Notre Dame, 1nd.

Filed: May 25, 1973 Appl. No.: 363,801

Inventor:

Assignee:

us. c1. 260/63 N; 117/128.4; 117/161 P; 161/227; 260/2.5 N; 260/47 cz; 260/47 cP; 260/47 UA; 260/49; 260/67 R; 260/72 R; 260/775 R; 260/78 TF; 260/78 UA; 260/78 sc 1m. c1 C08g 20/32 Field 61 Search 260/78 TF, 7s UA, 47 CP, 260/47 c2, 47 UA, 65, 78 SC, 49, 63 N References Cited UNITED STATES PATENTS 10/1963 Lavalou 260/78 3,322,729 5/1967 Grosser et al 260/78 Primary Examiner-Lester L. Lee

[57] ABSTRACT Aromatic polyimides with reactive end groups are cured by coupling together by addition or condensation to increase molecular weight with little or no byproduct formation. These polyimides can be shaped and formed prior to the coupling.

The aromatic polyimides appropriate for coupling are formed by the reaction of an aromatic dianhydride and an aromatic diamine in ratios to provide the appropriate end groups, or by including in the reaction mixture a compound which will provide reactive end groups, e.g., aromatic nitrile, allyl, propargyl, styryl, etc. Depending on the reactive end groups present, coupling of the polyimide is carried out either by self-coupling or by reacting the polyimide with a complementary organic compound. Included in the latter is the reaction with an aromatic bis-dipole compound which will propagate the polymer chain.

13 Claims, N0 Drawings PROCESS FOR, CIIAINTEXTENDING UNSATURATED'TERMINATED POLYIIMIDES AND PRODUCTS PREPARED THEREFROM BACKGROUND OF THE INVENTION U nation of by-products, to high molecular weight, thermally-stable polymers.

2. Prior Art The synthesis in recent years of a number of thermally-stable polymers (e.g. polyimides) has supplied materials whose properties allow them to meet some critical end-use requirements. Their application to other uses is limited by a number of their specific properties, among which is intractability. This necessitates their use in dilute solutions in such exotic solvents as sulfuric acid, for example, to be spun into fibers. This excludes their use in laminations and in moldings. In addition, once isolated from the solvent, high temperatures are required to convert them to the fully condensed or cured final state. This curing is accompanied by the elimination of volatile by-products.

In contrast, polymers containing oxirane structures. such as epoxy-phenolics, can be cured at reasonably low temperatures with a minimum of by-products. However, the thermal stabilities of the oxirane polymers fall below those, for example, of the stable polybenzimidazoles. Thus, it is desirable to prepare oligomers which will propagate to higher molecular weights with minimum volatile elimination at relatively low temperatures and which will possess thermal stabilities reasonably higher than epooxy phenolics, preferably approaching the stabilities demonstrated by the polyimides and similar polyheterocyclics.

SUMMARY OF THE INVENTION According to the present invention there is provided a polymeric chain-extending process comprising chainextending a polyimide of theformula:

O ll ll wherein v Ar is a tetravalent aromatic organic radical, the four carbonyl groups being attached directly to separate carbon atoms and each' pair of carbonyl groups being attached toadjacent carbon atornsin the Ar radical,

Ar is a divalent aromatic organic radical,

n is 0 when X and X are (l) or is a positive integer of at least one,

A is a terminal group selected from the group consisting of CH=CHR, C 5 CR, CN, CHO, OH, NH; and CH=NR" wherein R" is a monovalent aromatic organic radical of 6 to l2 carbon atoms,

R is a hydrocarbon radical of l to 12 carbon atoms,

and

by a coupling reaction selected from the group consisting of: I

l. self-coupling of said polyimide when A is CH=CHR, -C E CR, CN, or CH=NR", and

2. coupling said polyimide by reaction with a complementary organic compound, said compound being: a. when X and X are (2) and A is --Cl-I=CHR,

C CR, CN, CH=NR" or CHO, an aromatic bis-dipole of the formula Q Ar Q wherein Ar is a divalent aromatic radical and Q is selected from the group consisting of where R is an aliphatic or aromatic organic radical of l to 12 carbon atoms, b. when X and X are l a diisocyanate of the formula Ar(NCO) wherein Ar is a divalent aromatic organic radical, a diamine of the formula Ar(NI-I wherein Ar is a divalent aromatic organic radical or a diamine end-capped imide oligomer of the formula:

O O 0 ll ll ll ll wherein Ar and Ar and n areas defined above, and n is 0 or a positive integer of at least one,

c. X and X are (2) and A is --NH an aromatic di or tri anhydride, or its corresponding tetra or hexa carboxylic acid, and

d. when X and X are (2) and A is OH a compound selected from the group consisting of formaldehyde, a compound capable of generating formaldehyde under the reaction conditions and hexamethylene tetramine.

DETAILED DESCRIPTION OF THE INVENTION wherein Ar is atetraVaIent aromatic organic radical, preferably containing at least one ring of six carbon atoms, said ring characterized by benzenoid unsatura tionf the four carbonyl'groups being attached directly to separate carbon atoms and each pair of carbonyl groups being attached to adjacent carbon atoms in the Ar radical. Any of the aromatic tetracarboxylic acid dianhydrides known in the prior art can be used. Among the useful dianhydrides are 3,3',4,4-'benzophenonetetracarboxylic acid dianhydride, pyromellitic dianhydride, 2,3,6,7-naphthalene tetracarboxylic acid dianhydride, 3,3',4,4'-diphenyl tetracarboxylic acid dianhydride, l,2,5,6-naphthalene tetracarboxylic acid dianhydride, 2,2,3,3'-diphenyl tetracarboxylic aciddianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4,9, 1 O-perylene tetracarboxylic acid dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, naphthalene-l.2,4,5-tetracarboxylic acid dianhydride, naphthalene-l,4,5,8-tetracarboxylic acid dianhydride, decahydronaphthalene-l ,4,5,8-tetracarboxylic acid dianhydride, 4,8-dimethyl-l,2,3,5,6,7- hexahydronaphthalene-l,2,5,6-tetracarboxylic acid dianhydride, 2,6-dichloronaphthalenel ,4,5 .8- tetracarboxylic acid dianhydride. 2,7- dichloronaphthalenel ,4,5,8-tetracarboxylic acid dianhydride, 2,3,6,'l-tetrachloronaphthalene-l ,4,5,8- tetracarboxylic acid dianhydride, phenanthrenel,8,9,lO-tetracarboxylic acid dianhydride, cyclopenta- 4 ne 1 ,2,3 ,4-tetracarboxylic acid dianhydride, pyrrolidine-2,3,4,5-tetrac'arboxylic acid dianhydride, pyrazine- 2,3,5,6-tetracarboxylic acid dianhydride, 2,2-bis(2,3- dicarboxyphenyl )propane dianhydride, l, 1 -bis( 2,3- dicarboxyphenyl)ethan'e dianhydride, l,l-bis-(3,4- dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyUmethane dianhydride, bis(3,4-dicarbox'yphenyl)methane f dianhydride, bi's(3,4-dicarboxyphe,nyl)sulfone dianhydride, and benzene-l,2,3,4-

tetracarboxylic acid dianhydride. The first three mentioned dianhydrides are preferred.

Aromatic diamines useful in preparing the starting polyimides and in the process have the general formula:

whereih'Ar is a divalent aromatic organic radical. Preferred aromatic diamines are those wherein Ar is a divalent benzenoid radical selected from the group consisting of and multiples thereof connected to each other by R,

wherein R is an alkylene chainof 1-3 carbon atoms,

CI-I=CI-I, I

oxide, 4,4-diamino-diphenyl phenyl phosphine oxide,

4,4'-diamino-diphenyl N-methyl amine, 4,4'-diaminodiphenyl N-phenyl amine and mixtures thereof. 3,3- dimethyl-4,4'-diaminodiphenylmethane, 3,3" -diethyl- 4,4'-diaminodiphenylmethane, 3,3'-dimetho xy- 4,4'- diaminodiphenylmethane, 3,3-diethoxy'-4,4'- diaminodiphenylmethane, 3,3'-dichloro-4,4' ,4,4'- diaminodiphenylmethane, 3,3'-dibromo-4,4- diaminodiphenylmethane, 3,3'-dic'arboxy-4,4'- diaminophenylmethane, 3,3'-dihydroxy-4,4'- diaminophenylmethane, 3,3"-disulpho-4,4'- diaminodiphenylmethane, 3,3-dimethyl-4,4-

diaminodiphenylether, 3 ,3 '-diethyl-4,4'- diaminodiphenylether, 3,3 '-dimethoxy-4.4- diaminodiphenylether, 3,3'-diet'hoxy-4,4'- diaminodiphenylether, 3 ,3 -dichloro-4,4'- diaminodiphenylether, 3,3-dibromo-4,4-diamino diphenylether, 3,3 -dicarboxy-4,4- diaminodiphenylether, 3 ,3 -dihydroxy-4,4'- diaminodiphenylether, 3,3 di 1f -4,4'- diaminodiphenylether, 3,3 '-dimethyl-4,4'-

diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfide, diaminodiphenylsulfone, diaminodiphenylsulfone, diaminodiphenylsulfone, diaminodiphenylsulfone, diaminodiphenylsulfone, 4,4'diaminodiphenylsulfone, diaminodiphenylpropane, diaminodiphenylpropane, diaminodiphenylpropane, diaminodiphenylpropane, diaminodiphenylpropane, diaminodiphenylpropane, diaminodiphenylpropane, diaminobenzophenone, diaminobenzophenone, diaminobenzophenone,

3,3 -dimethoxy-4,4'- 3 ,3 '-diethoxy-4,4'-

3 ,3 -dichloro-4,4

3 ,3 '-dimethyl-4,4 3,3 '-diethoxy-4,4-

3 ,3 '-dichloro-4,4 3,3 '-dicarboxy-4,4'- 3 ,3 -dihydroxy-4,4'- 3,3 '-disulfo- 3,3 '-dimethoxy-4,4- 3 ,3 -dibromo-4,4'- 3,3 '-dichloro-4,4'- -dicarboxy-4,4'-

3,3 '-dihydroxy-4,4'- 3 ,3 '-disulfo-4,4

3 ,3 '-dimethyl-4,4 3,3 '-dimethoxy-4,4 3,3 -dichloro-4,4'-

3 ,3 '-dibromo-4,4-

diaminobenzophenone, 3,3 -dicarboxy-4,4- diaminobenzophenone, 3,3 -dihydroxy-4,4 diaminobenzophenone, 3,3- disulphodiaminobenzophenone, 3 ,3

diaminodiphenylmethane, 3,3-diaminodiphenylether, 3 ,3 '-diaminodiphenylsulfide, 3,3 diaminodiphenylsulfone, 3,3- diaminodiphenylpropane, 3,3-diaminobenzophenone, 2,4-diaminotoluene, 2,6-diaminotoluene, l-isopropyl- 2,4-phenylenediamine, 2,4-diaminoanisole, 2,4- diaminomonochlorobenzene, 2,4- diaminofluorobenzene, 2,4-diaminobenzoic acid, 2,4- diaminopheno], and 2,4-diaminobenzenesulfonic acid, and phenylene diamines. Preferred diamines are 4,4- oxydianiline, 4,4'-sulfonyldianiline, 4,4'-methylene dianiline, 4,4'-diaminobenzophenone, 4,4- diaminostilbene and the phenylene diamines.

The polyimide starting materials used in the process of the present invention are prepared according to the azeotroping process described in my copending application Ser. No. 363,800, filed even date herewith, the disclosure of which is hereby incorporated by reference. Briefly, the process involves reacting the dianhydride with the diamine in a phenol solvent of the formula where each R is hydrogen or a methyl radical in the presence of certain organic azeotroping agents, particularly cyclic hydrocarbons of 6 to 8 carbon atoms and most preferably benzene or toluene until most of the water of reaction is eliminated. A monoamine can also be used under certain conditions. T hereaction temperature is less than 140C. and also should be below the boiling point of the phenol usedbut higher than the boiling point of the azeotroping agent. The vapor phase temperature lies between that of the water azeotrope and no higher than C. As the water-of reaction and azeot'roping agent are removed from the reaction mixture, quantities of the azeotroping agent are returned to the reaction mixture so as to maintain the temperature and reaction mixture volume substantially" constant. It is preferred that the process'be continuous with continuous removal of water and continuous return of azeotroping agent. This is conveniently done by the use of a conventional Dean-Stark trap and condenser wherein after the azeotrope condenses, the water preferably sinks to the bottom of the trap for subsequent removal and the az'eotroping agent overflows the trap and returns to the reaction mixture. Initially, the trap is filled with azeotroping agent.

The polyimide starting material prepared by the above-described process will have the formula:

0 0 ll l X Ar-N Ar N X II i II wherein Ar and Ar are as defined previously, X is O i 0 ll II C C (l) O\ /Ar' /N C C II II o O 0 ll ll (2) ARN Ar N- t ll ll '0 O X' is II ll 0 when X is (l) or (2) RA,

n is 0 when X and X are (l) or is a positive integer of at least one, preferably at least 4 and usually in the range of 4 to 20,

A is a terminal group which is CH=CHR, C E CR, CN, -CHO, OH, NH or CH=NR" wherein R is a monovalent aromatic organic radical (phenyl, naphthyl, etc.),

R is a hydrocarbon radical of l to 12 carbon atoms,

and

R is H or R.

When the monoamine is not used in the azeotroping process, the polyimide starting material used in the present process will have two anhydride end groups when the molar ratio of dianhydride to diamine in the reaction mixture is m lzm or two amine end groups when the molar ratio of dianhydride to diamine is mm l where m is a positive integer of at least one and as high as n in the formula. Thus, the anhydride terminated polyimide will have the formula:

0 O O O O O 2 2 2 2 2 2 0 Ar N ArN Ar N ArN Ar 0 ll II II ll 0 O O O O O and the amine terminated polyimide can have the formula:

In this latter event R is also Ar.

When the molar ratio is dianhydride to diamine in the reaction mixture is m l:i m, two moles of a monoamine ARNH can be added to the reaction mixture to provide the terminal groups (A), i.e., CH=CHR, C E CR, CN, CHO, OH and CH=NR" wherein R is a monovalent aromatic radical. R is from H NC H CH CH=NC H CH Preferred monoamines are allyl amine, styryl amine, propargyl amine, aminobenzyl cyanide and aminobenzyl nitrile.

The chain-extending process used to make high molecular weight polyimides will depend on the particular terminal groups present. For example, when the terminal groups are CH=CHR, C E CR, CN or CH=NR", chain extension occurs by the selfcoupling of the starting polyimide. In particular, when the terminal groups are CI-I=CH such as when either allyl amine or styryl amine is used as the monoamine, chain extension occurs as in vinyl polymerization by thermal or free radical initiation. Initiation usually occurs by heating at a temperature of at least C., and less than 450C. In this situation, any of the free radical polymerization catalysts can be used, e.g., the peroxides such as benzoyl peroxide. A bis-maleimide can also be copolymerized with the CH=CH terminated polyimides. Bis-maleimides are known in the art and have the formula:

0 C") II ll 0 ll CH-C C-Cl-I 1| N ArN Ar N ArN H C ll 0 II ll 0 wherein Ar and Ar are as defined previously, and n is 0 or a positive integer of l to 20.

These bis-maleimides can also be prepared by the azeotroping process of my aforesaid copending application Ser. No. 363,800. Other monovinyl or multivinyl monomers such as the acrylics, allyl methacrylate, ethylene dimethacrylate, styrene, maleic esters and the like can also be copolymerized.

When the terminal groups are -C E CH, the polyimide can be chain-extended by catalytic polymerization in the presence of oxygen using a cuprous salt, e.g., cuprous chloride, cuprous sulfate, cuprous acetate, etc. Generally, about 0.1 to 5% by weight of the catalyst is sufficient.

Terminal groups which are CN or CH=NR" are polymerized using a catalytic amount of a Lewis acid salt, i.e., about 0.15 to 3 weight percent of AlCl SbCl SbCl or any others well-known as alkylation, isomeri- Zation or polymerization catalysts. For reasons of economy and handling, zinc chloride, zinc sulfate and the copper salts are preferred as the coupling catalysts.

Chain extension can also occur by coupling the starting polymide with a complementary organic compound. The particular organic compound used will depend on the particular terminal groups. For example, when the terminal groups are CH=CHR, C E CR, CN, .CHO, or CH=NR", one mole of the polyimide can be reacted with at least threefourths mole (preferably l-2 moles) of an aromatic bisdipole of the formula QArQ wherein Ar is a diva- 9 lent aromatic radical (phenyl, naphthyLetc.) and Q is c) Oi C V C v\ ArN\ /Ar\ 5 C CNO (nitrile oxide), -,CN=NR"' (nitrilimine), II II R"' O O C=NCHR"' (ylide) and CH=N\ (nitrone) n at least 4 is interjected between the maleimides, then the cycloaddition extension products have improved thermal where R is an aliphatic or aromatic organic radical stability. of l to 12 carbon atoms, preferably an aromatic radical The reaction between the bis-dipolar compound and G s 6 4( a) the reactive end group is a 1,3-dipolar cycloaddition The chemistry of the monofunctional dipole comreaction which does not eliminate by-products during pounds corresponding to the difunctional dipoles used 15 the course of propagation. For example, if styryl IS the in the present process is well known in the art. Synthereactive end group and l,4-benzenedinitrile oxide 18 ses of the monofunctional dipole compounds are exemused as the dipolar compound, the mode of propagaplified by Rolf Huisgen, Angew. Chem. Vol 75 (No. i n be shown as follows:

C C y N l N CH CH2 C C ll 0 o ONC CNO O 0 II II N i N CH CH2 0 C i C n O N O 0 13), pages 604-637 and 742-754, 1963, and in the Proceedings of the Chemical Society of London, Oct. 1961, pages 351-369. Many of the difunctional dipoles used in the present invention are synthesized by the same techniques described in thesereferences as well as in U.S. Pat. Nos. 3,390,204, 3,390,132 and 3,213,068. Preferred dipole compounds are 1,4- benzenedinitrile' oxide, l,4-benzenedi(phenylnitrilimine) and l,4-benaenedi(phenylnitrile ylide).

To increase the rate of reaction between the polyimide and bis-dipole, the concentration of the bisdipole can be increased up'to 2 moles. The reaction can take place at ambient temperatures or slightly higher, but once initiated, the temperature can go as high as the boiling point of' any solvent used, usually a phenol or the accepted aprotic polymer solvents disclosed in my copending application Ser. No. "363,800, filed same date.

The bis-m'aleimides described above are known to react with dipoles, but the thermal stability of the resulting product is low. I have discovered that if polyimide character, i.e.,

When the terminal groups are OH, the complementary organic compound is formaldehyde, a compound capable of generating formaldehyde under the reaction conditions such as paraformaldehyde or hexamethylene tetramine. The reaction is preferably carried out in the presence of lime as a catalyst with about I to weight percent lime, based on the weight of polyimide, usually being sufficient. The amount of formaldehyde used is usually in the range of about to by weight, based on the weight of polyimide, but can range from about 5 to by weight and even higher; however, there is usually no economic incentive for using higher concentrations.

The dianhydride terminated polyimides are chainextended by reacting them with an aromatic diisocyanate of the formula Ar(NCO) wherein Ar is a divalent aromatic organic radical preferably such as tolylene (CH C l-l xylylene (CH C H CH benzylene (C H CH phenylene (C H naphthylene (C, H diphenylene (C, l-l and generally any of the other Ar radicals listed with the aromatic diamines wherein Ar and Ar have been defined previously and,

n is a positive integer of at least 1, preferably .4 to 20. The reaction of the diamine and diamine terminated oligomer with the dianhydride preferably can be carried out at a temperature above the melting point of the materials involved or preferably in the phenol solvent defined previously, preferably m-cresol or a mixture of m-cresol with its other isomers, as well as in any of the accepted aprotic polymer solvents mentioned previously.

The diamine terminated polyimides are chainextended by reacting them with an anhydride of the formula wherein p is 2 or 3 and Ar is any of the radicals listed with the aromatic dianhydrides above when p is 2. When p is 3 Ar is a hexavalent aromatic organic radical, the six carbonyl groups being attached directly to separate carbon atoms and each pair of carbonyl groups being attached to adjacent carbon atoms in the Ar radical. Preferred anhydridesare mellitic dianhy-v dride. mellitic trianhydride and. 3,3, 4,4'-be nzophenonetetracarboxylic acid dianhydride.,T-his reaction can be carried out at a temperature above the melting point of the diamine terminated polyimide or preferably in any of the solvents defined previously (preferably m-cresol or a mixture of m-cresol and its isomers). Instead of the dior trianhydride, its corresponding tetra or hexa carboxylic acid can be used.

CO O

CO p The polyimides of the present invention have a number of uses. These include use of the solutions before curing as wire and insulating varnishes and to impregnate fabric substrates used in making flexible and rigid electronic circuit boards and in making structural laminates. The solutions can be used to make fibers and films and as adhesives, particularly for film substrates, useful in aerospace and electronics applications. The powders can be used as molding powders and to make fibers, films and foams.

The invention can befurthe'r understood by the following examples in which parts and percentages are by weight unless otherwise indicated.

EXAMPLE l a. Preparation of Amine-Terminated Oligomeric Polyimide (BTAT -3). Reaction 6f BTCA and ODA (7:8).

An apparatus consisting of a ml. three-neck, round-bottom flask "equipped with a magnetic stirrer, Dean-Stark trap and condenser, a dropping funnel, heating mantle, etc. isused in this and numerous following syntheses. For purposes of brevity, it will be called the m-cresolzbenz ene azeotropic apparatus.

In the m-cresolzbenzene azeotropic apparatus was placed 4,4'-oxydianiline (ODA) (3.204 g., 0.016 mole) in 20 ml. of m-cresol and 10 ml. of benzene. After warming to 60C., a solution of 3,3,4,4-benzophenonetetracarboxylic acid dianhydride (BTCA) (4.512 g., 0.014 mole) in 30 ml. m-cresol was added.

A copious yellow precipitate formed immediately. The

reaction mixture was heated to reflux and the solid material dissolved, forming an orange solution. After 2 hours of reflux, 0.30 ml. of water had been collected and a precipitate had formed in the reaction flask. After cooling, the reaction mixture was concentrated on a rotary flash evaporator and then vacuum-dried at 170C. to give 7.0960 g. (-100%) of a yellow solid which was slightly soluble in m-cresol, and insoluble in sulfolane and DMAC. On a Fisher-Johns melting point apparatus it softened slightly at about 210C., partially melted by 235C., and rehardened to a granular solid at 240C.

Analysis: Calcd. for C H N 0 C, 72.18; H, 3.10; N, 5.48. Found: C, 70.26; H, 3.26; N, 6.11.

b. Preparation of Oligomeric Anhydride (BTOD-l Reaction of BTCA and ODA (2:1

Into a 100 ml. three-neck, round-bottom flask equipped with a magnetic stirrer, thermometer, condenser, gas inlet tube, dropping funnel, etc. there was place,under nitrogen atmosphere, a solution of BTCA (6.444 g., 0.02 moleliii'25 ml-.of DM'AC.'Then-, a solution (if ODA (2.00 g., 0.01 mole) in 15 ml. of DMAC was addedov'er aperiod of 15 minutes. The reaction, whichwas exothermic, was maintained at 40C. during the addition, following which it was heated at 85-90C. far 15 minutes. To this=clear amber-colored solution, acetic'anhydride (3.06 g.'; 0.03 mole) was added and the mixture was heated'to C. Within 15 minutes, a yellow precipitate formed.- After heating, the reaction mixture for '1 hour,'the solvents were removed in a rotary flash evaporator. The residuallight-yellow solid was washed with anhydrous ether and dried in a vacuum oven at C, to afford a quantitative yield. lt softened slightly on .a Fisher-Johns melting point apparatus at ;l20C.- and did not melt when heated to 300C. The product was soluble in m-cresol aand N-methyl-Z-pyrrolidone and only slightly soluble in boiling benzonitrile, acetophenone or DMAC.

Its infrared spectrum shows the peaks for C=O of the anhydride group at 4.50 and 56311., and for the imide C=0, at 5.82u.

Analysis: Calcd. for C H N O C, 68.32; H, 2.49; N, 3.47. Found: C, 68.27; H, 2.82; N, 3.79.

c. Melt reaction of BTAT-3 and BTOD-l.

An intimate mixture of equimolar amounts of BTOD- l and BTAT-3 was placed between glass plates and placed on a block preheated to 250C. The sample melted and rehardened within 3 minutes. Then, as the temperature was raised at C./minute, the sample resoftened at 290C. and rehardened at about 325C.

EXAMPLE 2 V a. Preparation of Foamed Polyimide (BTFM-l Reaction of BTOD-l and Tolylene-2,4-diisocyanate (TDI) 1:1

An intimate mixture of BTOD-l prepared in Example l (b) (0.081 g., 0.0001 mole) and TDI (0.017 gl, 0.0001 mole) was prepared in a Wig-L-jig apparatus. A small sample of the mixture was placed between glass plates and placed onto a block preheated to 250C. The entire sample melted, foamed and hardened within 1 minute.

b. Preparation of Foamed Polyimide (BTFM-Z). Reaction of BTOD-l and TDI (1:2).

An intimate mixture of BTOD-l prepared in Example l (b) (0.81 g., 0.0001 mole) and TDI (0.034 g., 0.0002 mole) was prepared in a Wig-L-jig apparatus. A small sample of the mixture was placed between glass plates and placed onto a block preheated to 250C. The entire sample melted, foamed and hardened within seconds. The volume increase was noticeably greater in this case than (a) above.

EXAMPLE 3 a. Preparation of Styrene-Terminated Oligomeric Polyimide (BTAS-4). Reaction of BTCA, DAPB-3,3, ODA and AS in 9:(4:4):2 Mole Ratio.

In a large-scale m-cresolzbenzene azeotropic apparatus was placed, under a slow nitrogen sweep, BTCA (21.7505 g. 0.0675 mole), 175 ml. of m-cresol and 50 ml. of benzene. The mixture was warmed to approximately 70C. to dissolve the BTCA and then a solution of m-aminostyrene (AS) (1.7874 g., 0.015 mole) in 25 ml. of m-cresol, containing 0.1 g. of t-butyl catechol, was added over approximately one half hour. The solution was then refluxed for minutes. Then a solution of l,3-di( 3-aminophenoxy)benzene (DAPB-3,3) (8.7699 g., 0.030 mole) and ODA (6.0072 g., 0.030 mole) in 75 ml. of m-cresol was added. Reflux was maintained for 3 hours; 2.47 ml. of water was added. Then 50 ml. of benzene was distilled off.

After cooling to ambient temperature, the clear solution was added dropwise to 600 ml. of well-stirred methanol. After stirring for 2 hours, the solution was filtered. The isolated solid was heated in 200 ml. of boiling methanol containing approximately 0.1 g. of tbutyl catechol for 1 hour and filtered. The methanol wash was repeated three times. A small portion of the solid was removed and treated in boiling inhibitor-free methanol. This small sample was used for testing purposes, such as melting behavior, solubility, etc. The remainder of the material was vacuum-dried at ambient temperature for 40 hours, to give BTAS-4 as a yellow solid, 36.9 g. (103%). A TGA in nitrogen showed a loss of approximately 5% volatiles before an inflection point at approximately 510C. The sample was washed once more with hot methanol and vacuum-dried at 40C. for 16 hours to give 35.3 g. (98%). A TGA in nitrogen showed approximately 2% volatiles.

BTAS-4 was soluble in m-cresol and sulfolane, was partially soluble in hot DMAC and hot DMF, swelled slightly in dioxane, styrene, DVB and chloroform, but was insoluble in methanol and benzene. When heated from ambient to higher temperatures on a Fisher-Johns melting point block, BTAS-4 softened at l205C., was partially molten at approximately 220C., was a thick melt 235C, and hardened after 20 minutes at 300C. Its TGA in nitr gen showed an in flection point at approximately 510C. and a 58% residue at 1,000C. The DTA displayed an endotherm (softening or melting) in the region of 190C., which was followed immediately by a strong exotherm (polymerization) in the region of l210C., followed by a weak endotherm which blends into a second mild exotherm at approximately 260C. A 0.20 g. sample of BTAS-4 was heated in an air oven at 200C. for 5 hours to give BTAS-4-H200. The TGA of BTAS-4-H200 in nitrogen and in air showed the samples to be substantially free of m-cresol. The inflection points in nitrogen and in air are almost identical in the 500C. region; the difference in nitrogen and in air is found in a char residue of 60% to 0% respectively, at temperatures higher than 600C.

Analysis: Calcd. for C H N O C, 72.55; H, 3.12; N, 5.27; O, 19.06. Found: C, 72.54; H, 3.20; N, 5.32; O,

b. Reaction of BTAS-4 with ODA To a solution of BTAS-4 (0.4882 g., 0.0001 mole) in 14 ml. of m-c'resol was added a solution of ODA (0.020 g., 0.0001 mole) in 1 ml. of m-cresol. The solutions were mixed in a small flask and placed in an air oven at C. The temperature was raised slowly to 200C. over a period of 6 hours to eliminate solvent and maintained at 200C. for 24 hours. The cured product was obtained as dark-brown chips. The product was hard and tough, and required grinding in Wig-l-jig apparatus for 10 minutes to produce a powder, which was vacuum-dried at 200C. for 24 hours, to give 0.5091 g. (100%). Its infrared spectrum (KBr disc) was recorded. Its TGA in nitrogen and in air showed, in both cases, inflection points in the region of 500C. The product cured at 200C. was insoluble in boiling mcresol.

0. Thermal Polymerization of BTAS-4 in m-Cresol.

BTAS-4 (0.4882 g., 0.0001 mole) in 5 ml. of mcresol was heated according to the schedule given directly above to afford 0.4778 g. (98%) of dark glassy chips. Its infrared spectrum was recorded. Its TGA in nigrogen showed an inflection point in the 500C. region. The product cured at 200C. is insoluble in boiling m-cresol.

d. Thermal Catalyzed Polymerization of BTAS-4.

BTAS-4 (0.4882 g., 0.0001 mole) and benzoyl peroxide (0.005 g.) in 5 ml. of m-cresol were heated according to the schedule given above. There was obtained 0.4820 g. (99%) of a dark glassy solid. Its infrared spectrum was similar to that of cured BTAS-4.

EXAMPLE 4 a. Preparation of Styrene-Terminated Oligomeric Polyimide (BTAS-9). Reaction of BTCA, DAPB-3,3, and AS in 9:8:2 Mole Ratio.

In an m-cresol: benzene azeotropic apparatus was placed, under a slow nitrogen sweep, BTCA (2.175 g., 0.0675 mole), 10 ml. of m-cresol and 10 ml. of benzene. The-mixture was warmed to approximately 70C. to dissolve the BTCA and then a solution of AS (0.1787 g., 0.015 mole) in 25 ml. of m-cresol, contain ing 0.1 g. of t-butyl catechol, was added over approximately one half hour. The solution was then refluxed for minutes. Then a solution of DAPB-3,3 (1.7540 g., 0.060 mole) in 7.5 ml. of m-cresol was added. Reflux was maintained for 3 hours and then 10 ml. of benzene was distilled off.

After cooling to ambient temperature, the clear solution was added dropwise to 600 ml. of well-stirred methanol. After stirring for 2 hours, the solution was filtered. The isolated solid was heated in 200 ml. of boiling methanol containing approximately 0.1 g. of tbutyl catechol for 1 hour and filtered. The methanol wash was repeated three times. A small portion of the solid was removed and treated in boiling inhibitor-free methanol. This small sample was used for testing purposes, such as melting behavior, solubility, etc. The remainder of the material was vacuum-dried at ambient temperature for 40 hours, to give BTAS-9 as a lightyellow solid, 3.6 g. (92%).

BTAS-9 was soluble in m-cresol, DMAC, DMF, sulfolane, dioxane, chloroform and methylene chloride; it was partially soluble in hot tetrahydrofuran; it swelled in divinyl benzene. cis-1,2-dichloroethylene and methyl methacrylate and was insoluble in methylethyl ketone and trans-1,2-dichloroethylene. BTAS-9 melts in the l70205C. range, thickens above 210C. and rehardens at 230C.

A small sample was vacuum dried at 200C. to yield BTAS-9-H200 and analyzed.

Analysis: Calcd. for C l-l N O 2 C, 72.96; H, 3.21; N, 4.89; O, 18.94. Found: C, 73.04; H, 3.39; N, 4.64; O,

b. Catalyzed Polymerization of BTAS-9 EXAMPLE 5 a. Preparation of Styrene-Terminated Oligomeric Polyimide (NTAS-l Reation of 1 l,4,5,8-Naphthalenetetracarboxylic Acid Dianhydride (NTCA), DAPB-3,3 and AS (9:8:2).

Using the m-cresolzbenzene azeotropic apparatus procedure described previously, there was allowed to react 1,4,5,8naphthalene-tetracarboxylic acid dianhydride (NTCA) (2.8369 g., 0.01125 mole), DAPB-3,3

(2.9233 g., 0.01 mole) and AS (0.2979 g., 0.0025 mole). There was obtained NTAS-l 4.4712 g. (79.1%) as a tan powder which partially melted, with darkening at 220260C., rehardened at 265C., and then did not change up to 300C. When a sample was placed on a Fisher-Johns apparatus at approximately 220C., it became completely molten by 260C. and rehardened at about 265C.

NTAS-l was soluble in DMAC, m-cresol, sulfolane and concentrated sulfuric acid, and swelled in hot dioxane. lts infrared spectrum was consistent with that expected for the compound.

Analysis: Calcd. for c,,,,u,,,N,,o, C, 73.61; H, 3.15; N, 5.40; O, 17.83. Found: C, 73.74; H, 3.50; N, 5.83; O,

b. Catalyzed Polymerization of NTAS-l.

The oligomer, NTAS-l (0.250 g.) in 5 ml. of DMAC was cured with benzoyl peroxide (0.0025 g.) according to the schedule given in Example 4(b). There was obtained a dark granular solid (NTAS-l-cured). The polymer was insoluble in hot m-cresol.

EXAMPLE 6 a. Preparation of Nitrile-Terminated Oligomeric Polyimide BTAN-6. Reaction of BTCA, MDA-4,4 and AN (9:8:2).

In a m-cresolzbenzene azeotropic apparatus was placed (2,1751 g., 0.0135 mole) and 4- aminobenzonitrile (AN) (0.1772 g., 0.0030 mole) in 25 ml. of m-cresol and 10 ml. of benzene. The mixture was brought to reflux and maintained at reflux for 30 minutes. Then a solution of 4,4'-methylene dianiline (MBA-4,4) (1.1896 g., 0.0120 mole) in 15 ml. of mcresol was added and the mixture was refluxed for 30 minutes. At the end of the reflux period the theoretical amount of water had been collected and the reaction mixture was a clear yellow solution. Then the reaction mixture was added dropwise to approximately 100 m1. of methanol. The precipitated oligomer was digested three times in 100 ml. of hot methanol, filtered and vacuum-dried at C. for 24 hours. A pale yellow powder, BTAN-6, 2.1102 g. (94%) was obtained. On a Fisher-Johns melting point apparatus BTAN-6 melted over the range 230290C. the drop melt was 270C. It was soluble in m-cresol and sulfolane and became swollen in DMAC and dioxane.

b. Preparation of Nitrile-Terminated Oligomeric Polyimide BTAN-7. Reaction of BTCA, MDA-4,4, SDA-3,3 and AN (9:4+4:2).

According to the procedure reported in (a) above for the preparation of BTAN-6, there was allowed to react BTCA (2.9001 g., 0.009 mole), MDA-4,4 (0.7930 g., 0.004 mole), 3,3-sulfonyldianiline (SDA-3,3) (0.9932 g., 0.004 mole) and AN (0.2363 g., 0.002 mole). The reaction mixture was a clear yellow solution at the end of a 3-hour reflux period. After precipitation and vacuum-drying at 70C. for 24 hours there was obtained BTAN-7 as a pale yellow powder, 4.1594 g. (90.4%). On a Fisher-Johns apparatus BTAN-7 melted over the range 255285C. The drop melt was 260C. BTAN-7 was soluble in m-cresol, sulfolane and DMAC.

c. Preparation of Nitrile-Terminated Oligomeric Polyimide BTAN-8. Reaction of BTCA, MBA-4,4, SBA-3,3 and AN (9:6-l-2z2).

f. Curing of Nitrile-Terminated Oligomeric Polyimides,

BTAN-6 through BTAN-lO.

Intimate mixtures (-0.25 g.) of each of the nitrileterminated oligomeric polyimides, BTAN-6 through BTAN-lO with Cu Cl (5% by weight) were prepared in a Wig-L-jig apparatus. A single mixture of BTAN-6 with Cu- Cl was prepared similarly. Then samples of each of the mixtures were placed into' a test tube, the tube was flushed with nitrogen and capped with a nitrogen-filled balloon. The tubes were then placed into a metal block preheated to and electronically maintained at 300C. After 2 hours the tubes were removed and allowed to cool. Then the TGA in air and in nitrogen of each of the samples was performed at l0C./minute on a Du Pont 900. The pertinent data for these reactions are given in Table I.

TABLE I Data on Curing of Nitrilc-Terminated Oligomeric Polyimidcs BTAN-6 through BTAN-lO.

TGA Pcrccnt Residue at TGA Weight Weight Atmos- Break Inflec- Oligomcr g.) Catalyst g.) pherc 300C 400C. 500C. 600C. 700C. C. tion C.

BTAN-6 0.250 Cu Cl 0.0125 Air 100 95 0 0 0 365 STAN-6 0.500 Cu Cl 0.025 Air 100 98 8 0 0 360 BTAN-7 0.250 Cu- Cl 0.0125 Air 100 98 0 0 0 350 BTAN-8 0.250 Cu- .Cl 0.0125 Air 100 98 0 0 0 370 BTAN-9 0.250 Cu- Cl 0.0125 Air 100 88 0 0 0 340 BTAN-l0 0 250 (u- C]: 0.0125 Air 100 85 0 0 0 340 EXAMPLE 7 (1. Preparation of Nitrile-Terminated Oligomeric Polyimide BTAN-9. Reaction of BTCA, MBA-4,4, SDA-3,3 and AN (9:7+1:2).

The procedure reported in (a) above for the preparation of BTAN-6 was repeated using BTCA (2.9001 g., 0.009 mole), MBA-4,4 (1.3878 g., 0.007 mole), SDA- 3,3 (0.2483 g., 0.001 mole) and AN (0.2363 g., 0.002 mole). The reaction mixture remained clear during a 3-hour reflux period. There was obtained BTAN-9 as a pale yellow powder, 4.1670 (94%) which was soluble in m-cresol, partially soluble in hot sulfolane and insoluble in DMAC. On a Fisher-Johns apparatus BTAN-9 melted over the range 230290C. The drop melt was 280C.

e. Preparation of Nitrile-Terminated Oligomeric Polyimide BTAN-lO. Reaction of BTCA, MBA-4,4,

SDA-3,3 and AN (9:7.5+0.5:2).

The procedure reported in (a) above for the preparation of BTAN-6 was repeated using BTCA (2.9001 g., 0.009 mole), MBA-4,4 (0.4870 g., 0.0075 mole), SDA-3,3 (0.1242 g., 0.0005 mole) and AN (0.2363 g., 0.002 mole). At the end of a 3-hour reflux period the reaction mixture was slightly hazy. There was obtained BTAN-lO as a pale yellow powder, 4.1140 g. (93%), which was soluble in m-cresol, partially soluble in sulfolane and insoluble in DMAC. On a Fisher-Johns apparatus BTAN-lO melted over the range 250-280C. The drop melt was 270C.

A. Preparation of Amine Terminated Oligomers a. Preparation of Amine-Terminated Oligomeric Polyimide (BTAT-4). Reaction of BTCA and SBA-3,3 (4:5).

In a m-cresolzbenzene azeotropic apparatus was placed BTCA (11.2781 g., 0.035 mole), SDA-3,3 (10.8760 g., 0.0438 mole), ml. of m-cresol and 10 ml. of benzene. The mixture was refluxed for 3 /2 hours during which time 1.3 ml. of water was collected. Then, the benzene was distilled off and the solution was precipitated in methanol. The precipitated oligomer was digested three times in hot methanol and then vacuum dried at 70C. for 24 hours to give BTAT-4, 19.7498 g. as a light-yellow solid which was soluble in mcresol, DMAC and sulfolane. It swelled in hot dioxane. On a Fisher-Johns apparatus, it softened slightly above C., melted at 245280C. and rehardened after 5 minutes at 300C. The lowest temperature at which a sample would melt completely when dropped onto the preheated block was 270C.

A sample was vacuum-dried at 200C. and submitted for analysis.

Analysis: Calcd. for C H N O S C, 64.42; H, 2.87; N, 5.87; O, 20.12; S, 6.72. Found: C, 63.71; H, 2.91; N. 5.75; O, S,

b. Preparation of Amine-Terminated Oligomeric Polyimide (BTAT-S). Reaction of BTCA and SDA-3,3 (8:9).

According to the procedure used in (a) above, there wasallowed' to react BTCA (11.2781 g., 0.035 mole) and SDA-3,3 (9.7834 g., 0.0394 mole) in 80 ml. of mcresol and 10 ml. of benzene. There was obtained the oligomer, BTAT-S, as a light-yellow solid, 18.3 g.

(92.5%) which was soluble in m-cresol, DMAC and sulfolane. lt swelled in hot dioxane. On a Fisher-Johns apparatus it began to melt at 255C. but was not completely melted by 300C., at which temperature it hardened in 3 minutes. The lowest temperature at which a sample would melt completely when dropped onto the preheated block was 280C. 1 i

The analysis was performed on a small sample vacuum-dried at 200C.

Analysis: Calcd. for C H N O S C, 64.77; H, 2.76; N, 5.57; O, 20.51; S, 6.38. Found: C, 63.54; H, 2.81; N, 5.45; O, S, c. Preparation of Amine-Terminated Oligomeric Polyimide (BTAT-6). Reaction of BTCA and DAPB-3,3 (4:5).

According to the procedure in (a) above, BTCA (3.2223 g., 0.01 mole) and DAPB-3,3 (3.6529 g., 0.0125 mole) were allowed to react. There was obtained BTAT-6, 6.1215 g.'(94%) as a yellow powder. On a Fisher-Johns melting point apparatus BTAT-6 melted from l80-200C. and rehardened after 30 minutes at 300C. The lowest temperature at which a sample completely melted when dropped onto a preheated block was 190C. BTAT-6 was soluble in m-cresol, DMAC, sulfolane and dioxane.

A sample was vacuum-dried at 200C. for analysis.

Analysis: Calcd. for C H N O C, 72.81; H, 3.40; N, 5.37; O, 18.42. Found: C, 72.72; H, 3.35; N, 4.77; 0, i (1. Preparation of Amine-Terminated Oligomeric Polyimide (BTAT-7). Reaction of BTCA and DAPB-3,3 (8:9).

According to the procedure in (a) above, BTCA (3.2223 g., 0.01 mole) and DAPB-3,3 (3.2887 g., 0.01125 mole) were allowed to react. There 'was obtained BTAT-7 as a yellow powder, 5.8708 g. (95.4%). On a Fisher-Johns apparatus BTAT-7 began to inch from 190C. but did not completely melt by 300C., when it hardened in 30 minutes. The lowest temperature at which a sample melted when dropped onto a preheated block was 220C. BTAT-6 was soluble in mcresol, DMAC, sulfolane and dioxane.

A small sample was vacuum-dried at 200C. for analysis.

Analysis: Calcd. for C H N O C, 72.74; H, 3.28; N, 5.12; O, 18.86. Found: C, 72.45; H, 3.31; N, 5.04; O,

B. Preparation of Anydride-Terminated Oligomers a. Preparation of Anhydride-Terminated Oligomeric Polyimide (BTOD-3). Reaction of BTCA and SDA-3,3 (:4).

According to the procedure used in A(a) above, there was allowed to react BTCA (12.0827 g., 0.0375 mole) and SDA-3,3 (7.4493 g., 0.03 mole) in 80 ml. of m-cresol and 10 ml. of benzene. There was obtained the oligomer BTOD-3, as a light-yellow solid, 16.9 g. (92%) which was soluble in m cresol, DMAC, DMF and sulfolane. It softened at 240C., melted from 245265C., with the evolution of small amounts of gas, and did not harden during 30 minutes at 300C. The lowest temperature at which a sample melted completely when dropped onto a preheated block was A Small sample was vacuum-dried at 200C. and sub mitted for analysis.

. 2 Analysis: CalCd. C13;;H62 ,N1O35S4 H, 2.56; N, 4.01; O, 22.89; S, 5.24. Found: C, 63.90; H, 2.74; N, 4.70; O, S, b. Preparation of Anhydride-Terminated Oligomeric Polyimide (BTOD-4). Reaction of BTCA and SBA-3,3 (9:8). I

According to the procedure used in A(a) above, there was allowed to react BTCA (14.5003 g., 0.045 mole) and SDA-3,3 (9.9324 g., 0.04 mole) in m1. of m-cresol and 20 ml; of benzene. There was obtained the oligomer, BTOD-4, as a light-yellow solid, 21.4 g. (%)which was soluble in m-cresol, DMAC, DMF and sulfolane. It began to melt at 265C. with the evolution of small amounts of gas, but was not melted completely by 300C. and did not harden during 15 minutes at 300C. The lowest temperature at which a sample melted completely when dropped onto a preheated block was 270C.

A small sample vacuum-dried at 200C. was submitted for analysis. 7

Analysis: Calcd. for C H N O S C, 65.24; H, 2.60; N, 4.58; O, 21.99; S, 5.60. Found: C, 63.99; H, 2.73; N, 4.95; O, S, v c. Preparation of Anhydride-Terminated Oligomeric Polyimide (BTOD-S). Reaction of BTCA and DAPB- 3,3 (5:4).

According to the procedure used in A(a) above, there was allowed to reactBTCA (4.0279 g., 0.0125 mole) and DAPB-3,3 (2.9223 g., 0.01 mole) in 40 ml. of m-cresol and 10 ml. of benzene. There was obtained the oligomer BTOD-S (5.7678 g., 80%) as a lightyellow powder which was soluble in m-cresol, DMAC, sulfolane and dioxane. On a Fisher-Johns melting point apparatus BTOD-S melted over the range of -205C. with gas evolution and did not harden during 10 minutes at 300C. The lowest temperature at which a sample melted completely when dropped onto a preheated block was 200C.

Analysis: Calcd. for Cg -,H N O C, 71.52; H, 2.98; N, 4.25; O, 21.24. Found: C, 71.41; H, 3.2l; N, 4.46; o, Y

d. Preparation of Foamed Polymer by Reaction of a Diisocyanateand an Oligomeric Anhydride Terminated Polyimide.

The procedure of Example 7B(c) was used to prepare an oligomerof BTCA and DAPB-3,3 in a 9:8 mole ratio (BTOD-ZO).

A mixture of oligomer (BTOD-20) (0.5495 g., 1 X 10" mole) and TD] (0.0522 g., 3 X 10 mole) was packed tightly into a pyrex tube. The tube was then flushed well with nitrogen gas, and a balloon, which was'filled with nitrogen gas, was attached to the pyrex tube. The tube was then-inserted into a thermostatically controlled metal block, preheated to 225C., causing the mixture to form a foamed structure within a few minutes, which did not collapse when heating was continuted for 3 hours. A sample of the foamed product was insoluble in cold 'm-cresol but swelled in hot mcresol. The foamed product was then heated at 300C. in air over 2 hours whose TGA in air showed an inflection point in the 525C. region. In nitrogen the clear residue at 1,000C. amounted to 60%.

C. Preparation of Polyimide Polymer Components Intimate mixtures of the various reactants prepared in A. and B. above and BTCA, SDA-3,3 and mellitic trianhydride (MTA) were prepared for polymerization their components are listed in Table 11.

TABLE 11 Components Used in the Preparation of PlB-Type Polymers Components Polymer Amine or Amine- Anhydride or Anhydride- Terminated Oligomer Terminated Oligomer Crosslinking Agent (grams moles) (grams moles) (grams moles) BTAT-4 BTOD-3 PlB-l 0.2393 g.. 0.0001 m 0.2446 g., 0.0001 m none BTAT-4 BTOD-3 BTAT-4 PlB-lA 0.2393 g.. 0.0001 in 0.2446 g., 0.0001 in 0.0239 g.. 0.00001 m BTAT-4 BTOD-3 BTAT-4 PlB-lB 0.2393 g.. 0.0001 m 0.2446 g.. 0.0001 m 0.1 196 g. 0.00005 m BTAT-4 BTOD-3 BTAT-4 PlB-lC 0.2393 g.. 0.0001 rn 0.2446 g.. 0.0001 m 0.2393 g.. 0.0001 in BTAT-4 BTOD-3 SDA 3.3 PlBlD 0.2393 g., 0.0001 In 0.2446 g.. 0.0001 n1 0.0025 g., 0.00001 m BTAT-4 BTOD-3 SDA-3.3 PlB-lE 0.2393 g. 0.0001 m 0.2446 g.. 0.0001 m 0.0125 g.. 0.00005 m BTAT-4 BTOD- 3 SDA- 3 .3 PlB-lF 0.2393 g., 0.0001 m 0.2446 g.. 0.0001 in 0.025 g, 0.0001 m BTAT-S BTOD-4 P18 2 0.2268 g.. 0.00005 m 0.2289 g.. 0.00005 m none BTAT-S BTOD-3 PIE-3 0.4524 g.. 0.0001 rn 0.2446 g. 0.0001 in none 13TAT4 BTOD-4 PlB-4 0.2262 g., 0.00005 m 0.2290 g.. 0.00005 rn none SDA-3.3 BTOD-3 PlB-S 0.0496 g.. 0.0002 in 0.4892 g, 0.0002 m none SDA-3,3 BTOD-4 P1B-6 0.0248 g.. 0.0001 m 0.4584 g., 0.0001 m none STAT-4 BTCA P1B-7 0.4772 g.. 0.0002 in 0.0644 g., 0.0002 m none BTAT5 BTCA PlB-8 0.4524 g. 0.0001 m 0.0322 g.. 0.0001 in none BTAT-4 MTA FIB-9 0.5011 g.. 000021 in none 0.0403 g.. 0.00014 m BTAT-S MTA PlB-l 0.4072 g., 0.00009 in none 0.0173 g.. 0.00006 m BTAT-6 BTOD-S PlB-ll 0.2606 g., 0.0001 m 0.2636 g., 0.000] in none BTAT-7 BTODS PlB-l2 0.2460 g.. 0.00005 rn 0.2476 g.. 0.00005 m none STAT-7 BTOD- PlB-l3 0.4920 g., 0.0001 in 0.2636 g., 0.0001 m none BTAT-6 BTOD-6 PlB-l4 0.2606 g., 0.0001 rn 0.4952 g.. 0.0001 m none DAPB-3,3 BTOD-S PlB-lS 0.0584 g., 0.0002 in 0.5272 g, 0.0002 in none DAPB-3,3 BTOD-6 FIB-16 0.1922 g.. 0.0001 in 0.4952 g., 0.0001 m none BTAT-6 BTCA PlB-l7 0.5212 g.. 0.0002 in 0.0664 g.. 0.0002 m none BTAT-7 BTCA FIB-18 0.4920 g.. 0.0001 in 0.0322 g, 0.0001 in none BTA'I 6 MTA PIE-l9 0 5212 g.. 0.0002 m none 0.0384 g.. 0.000133 m BTAT-7 MTA FIB- 0.4920 g.. 0.0001 In none 0.0192 g.. 0.000067 m D. Preparation of Polyimides By Melt Reaction Small portions of the mixtures prepared in C. above were placed between glass slides and then the slides were dropped onto a preheated, electronically thermostatically controlled metal block. The samples were observed for 15 minutes and then removed. Observations in melting behavior, rehardening and solubility in mcresol are given in Table 111. Then the temperature of the metal block was raised and similar observations were made both on the samples preheated for 15 minutes and on new samples. These observations are also given in Table 111. The suffix M designates the polymer as prepared by a melt reaction.

E. Preparation of Polyimides By Solution Reactions Weighed samples (0.25 g.) of each of the mixtures TABLE 111 Data and Observations on the Preparation of PlB-Type Polyimides by Melt Reactions Observations (sample from T at T;

New Sample at T cresol partial melt. hard in 20 min., slightly swollen in hot m-eresol partial melt. hard in 15 min., swollen in hot mcresol complete melt. hard in 3 min., swollen in hot mcresol complete melt. hard in 5 min., swollen in hot mcresol Polymer prepared in C. above were added to 2.5 ml. of solvent and allowed to stand at ambient temperature for 24 hours with occasional swirling. Then the samples were treated to one of the heating schedules given below.

LII

Heating Schedule A.

The solutions were heated in an air oven at 100C. for 15 minutes. Precipitation did not occur. Then the samples were heated in an air oven at 100C. for 3 hours; then at 150C. for 24 hours; and finally at 200C. for 24 hours. Then. small portions of the films obtained were dried in an air oven at 300C. for 20 hours. The observations are given in Table IV in which the suffix TABLE 111 -Continued at T.

slightly melted, rehardened immediately. swollen in hot m-cresol complete melt with applied pressure. hard in 10 min.. soluble in hot mcresol complete melt. hard in 5 min.. swollen in hot mcresol complete melt. hard in 5 min.. swollen in hot mcresol complete melt. bubbled. hard in 5 min.. partially soluble in hot m-cresol partial melt. hardened immediately. swollen in hot mcresol partial melt. hard in 3 min.. swollen in hot mcresol partial melt. hard in 3 min.. soluble in hot mcresol complete melt. bubbled. hard in 15 min. complete melt. bubbled. hard in min. complete melt. bubbled. hard in 20 min. complete melt. bubbled. elastic. not hard in 1 hour complete melt. bubbled. hard in 6 min.

complete melt. bubbled. hard in 10 min. complete melt. bubbled. hard in 40 min. complete melt. bubbled. hard in 30 min. complete melt. bubbled. hard in 1 hour complete melt. hard in 1 hour Observations (sample from T,) at T;

partial melt. hard in 20 min.. swollen in hot mcresol partial melt. hard in 20 min.. swollen in hot mcresol partial melt. hard in min.. swollen in hot mcresol partial melt. hard in min.. swollen in hot mcresol complete melt. bubbled. hard in min.. swollen in hot mcresol slow partial melt. hard in 25 min.. slightly swollen in hot m-cresol slight melt. hard in 5 min.. swollen in hot m-cresol slight melt. hard in 5 min.. swollen in hot m-cresol softened. remained elastic for 90 min.

complete melt. bubbled. elastic for 90 min. complete melt. remained elastic for 90 min. complete melt. remained elastic for 90 min. slightly melted. hard in min.

partial melt. bubbled. elastic for 90 min. complete melt. few bubbles. elastic for 90 min. complete melt. elastic for 90 min.

slightly melted. elastic for 90 min.

partial melt. hard in 1 hour Table V.

Data and Observations on the Preparation of PlB-Type Polyimides by Melt Reactions New Sample at T complete melt. hard in 5 min.. slightly swollen in hot m-cresol complete melt. hard in 5 min.. slightly swollen in hot m-cresol complete melt. bubbled, hard in 15 min.. swollen in hot m-cresol complete melt, bubbled. hard in 10 min.. swollen in hot m-cresol complete melt. bubbled. hard in 90 min.. swollen in hot m-cresol complete melt. bubbled. hard in 5 min.. slightly swollen in hot m-cresol partial melt. bubbled. hard in 5 min.. swollen in hot m-cresol partial melt. hard in 5 min.. swollen in hot mcresol complete melt. bubbled. elastic for 90 min.

complete melt. bubbled. elastic for 90 min.

complete melt. bubbled. elastic for 90 min.

complete melt. bubbled. elastic for 90 min.

complete melt. bubbled. hard in 20 min.

complete melt. bubbled. elastic for 90 min.

complete melt. bubbled. elastic for 90 min. complete melt. bubbled. elastic for 30 min.

complete melt. few bubbles. hard in 30 min.

complete melt. bubbled. elastic for 2 hours S designates the polymer as one prepared in solution. TGA data for selected FIB-type polyimides is given in Heating Schedule B.

The solutions were heated at C. for 30 minutes.

TABLE IV Data and Observations on the Preparation of PlB-Type Polyimides in Solution Polymer Solvent Heating Observations Schedule deep red smooth film. good adhesion to glass PlB-l-S m-cresol A vessel.

very dark red smooth film. better adhesion PIBJA-S m-cresol A to glass than PlB-l-S very dark red smooth film. better adhesion to PlB-lB-S m-cresol A glass vessel than PlB-l-S very dark red smooth film. better adhesion PlB-lC-S m-cresol A to glass vessel than PlB-l-S very dark red smooth film. better adhesion PlB-l D-S m-cresol A to glass vessel than PlB-l-S very dark red smooth film. better adhesion PlB-lE-S m-eresol A to glass vessel than PlBl-S verv dark red smooth film. less adhesion Data and Observations on the Preparation of PlB-Type Polyimides in Solution Polymer Solvent Heating Observations Schedule PlB-lF-S m-cresol A to glass vessel than PlB-l-S deep red smooth film. good adhesion to PlB-2-S m-eresol A glass vessel deep red smooth film. good adhesion to PlB-3-S m-eresol A glass vessel lighter red smooth film. good adhesion PlB-4-S m-cresol A to glass vessel deep red smooth film. good adhesion to PlB-S-S m-cresol A glass vessel lighter red smooth film. good adhesion to PlB-6-S m-cresol A glass vessel lighter red smooth film. good adhesion to PlB-7-S m-cresol A glass vessel very deep red smooth film. good adhesion PlB-S-S m-cresol A to glass vessel dark-brown smooth film. good adhesion to PlB-9-S m-cresol A glass vessel dark-brown smooth film. with small amount of PlB-l-S m-eresol A very lline particles. good adhesion to glass vesse H100: good yellow film: H180: melted. PlB-l l-S dioxane B bubbled. hardened in 10 506.. H200: foamed.

tough film H100: some solid in yellow film. H180: PlB-l2-S dioxane B melted. bubbled. hardened in min.: H200:

H100: some solid in yellow film; H180: PlB-l3-S dioxane B melted. bubbled. hardened in 1 min.: H200:

foamed. tough film H100: good yellow film; H180: melted. PlB-l4-S dioxane B bubbled. hardened in l min.: H200: foamed.

H100: good yellow film: H180: melted. PlB-lS-S dioxane B bubbled. hardened in 1 min.: H200: foamed.

Hl00: good yellow film: H180: melted. PlB-l6-S dioxane B bubbled. hardened in l min.; H200: foamed.

H100: good yellow film: H180: melted. PlB-l7-S dioxane B bubbled. hardened in l min.: H200: foamed.

H100: good yellow film: H180: melted.

PlB-lll-S dioxane B bubbled. hardened in l min.; H200: foamed.

solution gelled in V; hrs. H100: good yellow PlB-lQ-S dioxane B. film: H180: softened. not hard in 1 hr.:

H200: few bubbles. tough film solutiongelled in A hr.; H100: good yellow PlB-20-S dioxane B film: H180: softened. not hard in 1 hr.:

H200: few bubbles. tough film was heated-at 200C. for 72 hours and then cooled. Obious substrates either by applying the solution with a servations on the products are given in Table IV. Suffix small camels hair brush or by dipping, and then cured S indicates a solution reaction. TGA data for selected by heating the coated articles in a forced oven at C. PlB-type polyimides is given in Table V. for 20 hours, 1001 10C. for 3 hours and then 200C.

. TABLE V TGA Data for Selected PlB-Type Polylmides 'TGA: Percent Residue at Polymer phere 200C 0 300C 400C 500C 600C 700C 800C PlB-l-S Air 100 98 94 89 67 0 0 PlB-lF-S Air 100 9 9 95 92 73 0 0' PlB-4-S Air 100 97 89 70 12 0 PlB-S-S Air 100 100 97 93 78 0 0 PlB-9-S Air 100 98 92 89 70 0 0 PlB-l l-S Air 100 100 99+ 99 76 0 0 PlB-l7-S Air 100 100 99 98 83 10 0 PlB-l9-S Air 100 100 98 97 82 13 0 g 65 F. Coating of substrat for 20 hours. Substrates coated were stainless steel and aluminum panels, 100 pores/inch reticulated polyure- Solutions PlB-l7-S and PlB-19-S were coated on varthane foam, 5 random glass mat, copper wire EXAMPLE 8 a. Synthesis of Propargyl-Terminated Oligomeric Polyimide (BTPA-l Reaction of BTCA, ODA and Propargyl Amine (2:1 :2).

In a m-cresolzbenzene azeotropic apparatus was placed a solution of BTCA (29.001 g., 0.09 mole) in 200 ml. of m-cresol and 50 ml. of benzene. The mixture was warmed to approximately 50C. and a solution of ODA(9.011 g., 0.045 mole) in 150 ml. of m-cresol was added, forming a slight amount of yellow precipitate. After minutes, a solution of propargyl amine (5 g., 0.0908 mole) in ml. of m-cresol was added and the solution heated to reflux. During 2 hours of reflux, 3.3 ml. of water was collected. After cooling, the deep red solution was concentrated on a rotary flash evaporator.

A small sample was removed for analysis and approximately 5 mg. of t-butyl catechol was added to the bulk of the residue, which was vacuum-dried at C, for 30 hours, and then C. for 12 hours, to give sample A, 37.850 g. (95%) as a dark-brown solid. lt softened at 270C.; partially melted between 280300C., but quickly rehardened at 300C.

Analysis: Calcd. for C H N O C, 70.75; H, 2.97;

N, 6.35; O, 19.94. Found: C, 70.84; H, 3.13; N, 6.31; O

b. Polymerization of BTPA-l.

A sample of BTPA-l was mixed with about 5% by EXAMPLE 9 a. Preparation of Phenolic-Terminated Oligomeric Polyimide (BTAP-l Reaction of BTCA, ODA and p-Aminophenol (2:1:2).

1n the m-cresol:benzene azeotropic apparatus was placed a solution of BTCA (3.222 g., 0.01 mole) in 25 ml. of m-cresol and 15 ml. of benzene. After warming to 50C.. a solution of ODA (1.001 g., 0.005 mole) in 15 ml. of m-cresol was added, forming an immediate yellow precipitate. Further heating did not dissolve the precipitate, and, after 10 minutes, a slurry of freshly purified p-amlnophenol (m.p. 190193C.; 1.019 g., 0.01 mole) in 10 ml. of m-cresol was added. At reflux, the solid dissolved forming an orange solution. During 2 hours of reflux, 0.20 ml. of water was collected and a precipitate formed. Then, the solvents were removed on a rotary flash evaporator and the residue was vacuum-dried at C., yielding a yellow solid, 4.907 g. (99%). Its infrared spectrum was consistent with the structure expected for the compound. 1t softened slightly at 50C.. was almost completely melted at 265-280C.; and rehardened at 283C. It was soluble in hot m-cresol, hot DMAC and hot sulfolane.

6 Analysis: Calcd. for C ,,H N,,O C, 70.30; H, 3.05;

N, 5.65; O, 20.99 Found: C, 70.04; H, 3.01; N, 5.73;

LII

b." Polymerization of BTAP-l.

A mixture,of BTAP-l with about 10-12% paraformaldehyde and l5% lime cures into an insoluble, in-

5 tractable polymer when heated at the melting point of BTAP-l on a hot plate.

EXAMPLE 10 a. Preparation of Phenol-terminated Oligomeric Polyimide (BTAP-4). Reaction of BTCA, SBA-3,3 and p-Aminophenol According to the m-cresolzbenzene technique there was allowed to react BTCA (6.446 g., 0.02 mole),- SBA-3,3 (3.9730 g., 0.016 mole) and p-aminophenol (0.8730 g., 0.008 mole). There was obtained 10.0418 g. (95%) of a pale yellow powder (BTAP-4) which was soluble in m-cresol, DMAC and sulfolane. In hot dioxane BTAP-4 formed a separate oily layer. On a Fisher- .Iohns melting point apparatus BTAP-4 softened at 210C., melted at'240260C. and did not harden on being heated at'300C. for 40 minutes. The lowest temperature at which a sample would melt completely when dropped onto the preheated stage was 250C.

Analysis: Calcd. forC l'l N O S C, 65.90; H, 2.75;N, 5.30; O, 21.19; S, 4.85. Found: C, 65.45; H, 2.88; N, 4.99; O,; S, C, 65.43; H, 2.95; N, 5.31;

O; S, I

b. Polymerization of BTAP-4.

A mixture of BTAP-4 with about 1012% paraformaldehyde and l-5% lime cures into an insoluble, intractable polymer when heated at the melting point of BTAP-4 on a hot plate.

c. Preparation of Aldehyde-Terminated Oligome r.

When an equivalent molar quantity of paminobenzaldehyde, NH C H CHO (0.968 g.) is used instead of the p-aminophenol of (a) of this Example, the corresponding aldehyde-terminated oligomeric imide is obtained.

Similarly, when an equivalent molar amount of p-arninobenzylidene-aniline, NH C H CH=NC H (1.568 g.) isused instead of the p-aminophenol of (a) of this Example, the corresponding Schiff baseterminated oligomer is obtained. The amino-aryl Schiff bases were readily prepared by the procedure give by Rossi in Gazz. chim., ltal., 44, 263 (1966).

d. Coupling ofSchiff Base-Terminated Oligomer.

The Schiff base-terminated olifomers as in (c) of this Example couple similarly to the nitrile terminated oligomers of Example 6. They couple readily when heated in the range of 200300C. for 30 minutes to 2 hours, depending on the nature of the oligo mer'and EXAMPLES 11-56 A. Preparation of lmide Oligomers a. Preparation of Aromatic Nitrile-Terminated Oligomeric Polyimide (BTAN-2). Reaction of 3,3',4,4'- Benzophenonetetracarboxylic Acid Dianhydride (BTCA), 4,4'-Oxydianiline (ODA) and 4- Aminobenzonitrile (AN) (2:1:1).

1n the m-cresolzbenzene azeotropic apparatus there was placed a solution of 3,3,4,4'-benzophenonetetracarboxylic acid dianhydride (BTCA) (3.222 g., 0.01 mole) in 25 ml. m-cresol and 15 ml. benzene. The mixture was warmed to approximately 50C. and a solution of 4,4-oxydianiline (ODA) (1.001 g., 0.005 mole) in 15 ml. of m-cresol was added, giving an immediate yellow precipitate. After 15 minutes, a solution of 4- aminobenzonitrile (AN) (1.299 g., 0.011 mole) in ml. of m-cresol was added. During 2 hours of refluxing, the solution became orange and 0.25 ml of water was collected. Precipitation did not occur. After cooling, the solvents were removed on a rotary flash evaporator and the residue was vacuum-dried at 100C. to yield 5.177 g. 102%) of phenylnitrile-terminated oligomeric polyimide based on BTCA (BTAN-Z). On a Fisher- Johns melting point apparatus, 230C. was the lowest temperature at which it softened before rehardening immediately. It was soluble in hot m-cresol, slightly soluble in hot dimethyl acetamide (DMAC), and insoluble in hot acetone. A sample of BTAN-2 was post-heated in nitrogen at 300C. for 24 hours, and its TGA in nitrogen of sample BTAN-2-l-l300, showed an inflection point at 410C.

Analysis: Calcd. for C H N O C, 71.43; H, 2.80; N, 8.03; O, 17.44. Found: C, 70.83; H, 2.81; N, 7.77; O, Found: C, 71.22; H, 2.86; N, 7.93; 0, (dried at 140C.)

b. Preparation of Aromatic Nitrile-Terminated Oligomeric Polyimide (BTAN-3). Reaction of BTCA, 3,3- Sulfonyldianiline (SDA-3,3) and AN (9:8:2).

In the m-cresolzbenzene azeotropic apparatus there was placed a solution of BTCA; (2.1750 g., 0.00675 mole) in 25 ml. of m-cresol and 10 ml. of benzene. The solution was warmed to approximately 70C. and a solution of AN (0.1773 g., 0.0015 mole) in 10 ml of mcresol was added over about 20 minutes. After stirring at approximately 70C. for minutes, a solution of 3,3-sulfonyldianiline (SBA-3,3) (1.4899 g., 0.0060 mole) in 15 ml. of m-cresol was added and the solution was heated to reflux for 3 hours, during which time, 0.3 ml. of water was collected; then the benzene was distilled off and after cooling to room temperature, the solution was added dropwise slowly to 200 ml. of wellstirred methanol, to yield a light-yellow solid. The solid was filtered off, digested four times in hot methanol, and dried at 40C. for 24 hours, to give 3.40 g. (95%) of yellow product. The yield, corrected for about 2% retained m-cresol, was 93.5%. The oligomer partially melted at 255C. and rehardened at 275C; it was soluble in m-cresol, DMAC and hot sulfolane, but insoluble in dioxane. A small sample, vacuum-dried at 200C. for 4 hours, showed at 2% loss of m-cresol, which was confirmed in its TGA in nitrogen, which also shows an inflection point in nitrogen in the 500C. region. lts DTA in nitrogen shows an endotherm at 225C.

Analysis: Calcd. for C H N O S C, 65.83; H, 2.65; N, 5.84; O, 20.34; S, 5.35. Found: C, 65.29; H, 2.70; N, 5.36; O, S,

The above procedure was repeated except that the quantities used were increased to yield 33.0 g. (97%) of BTAN-3. The quantities used were BTCA, 21.7505 g., 0.0675 mole; SDA-3,3, 14.899 g., 0.060 mole; AN, 1.7172 g., 0.0150 mole. 0. Preparation of Aromatic Nitrile-terminated Oligomeric Polyimide (BTAN-4). Reaction of BTCA, 1,3-Di(3-Aminophenoxy)benzene (DAPB-3,3) and AN (9:8:2).

In the m-cresol:benzene azeotropic apparatus there was placed a solution of BTCA (2.1753 g., 0.00675 mole) in 25 ml. of m-cresol and 10 ml of benzene. The solution was warmed to approximately C. and a solution of AN (0.1773 g. 0.0015 mole) in 10 ml. of mcresol was added over about 20 minutes. After stirring for another 15 minutes, a solution of 1,3-di(3-aminophenoxy)benzene (DAPB-3,3) (1.7540 g., 0.0060 mole) in 15 ml of m-cresol was added. The solution was heated to reflux for 3 hours and 0.2 ml of water was collected. Then the benzene was distilled off. After cooling, the clear solution was added dropwise to 200 ml of methanol. The precipitated solid was digested three times in hot methanol and vacuum-dried at 70C. to give BTAN-4, as a light-yellow solid, 3.4 g. (88%).

The infrared spectrum (KBr disc) of BTAN-4 is given in FIG. 29; it was soluble in m-cresol, DMAC, sulfolane, dioxane; because a paste in methylene chloride, swelled in chloroform and was insoluble in acetonitrile. BTAN-4 softened at 180C., melted over the range of l972l8C., thickened above 290C., but did not harden within 20 minutes at 300C, although it did darken somewhat. For the sample dried at 70C., the DTA in nitrogen showed a melting endotherm at about 180C.

A sample of BTAN-4, vacuum-dried at 200C., to eliminate volatiles, was submitted for analysis.

Analysis: Calcd. for C H N O C, 72.13; H, 3.14; N, 5.52; O, 19.22. Found: C, 72.41; H, 3.28; N, 5.1 1; O,

d. Synthesis of Allyl-terminated Oligomeric Polyimide (BTAA-3). Reaction of BTCA, ODA and Allylamine (2:122).

In the m-cresolzbenzene azeotropic apparatus, there was placed a solution of BTCA (3.222 g., 0.01 mole) in 25 m1. of m-cresol and 15 ml. of benzene. The solution was warmed to approximately 60C. and a solution of ODA (1.001 g., 0.005 mole) in 15 ml. of m-cresol was added, forming an immediate yellow precipitate which dissolved on heating further for 5 minutes. Then, a solution of allylamine (0.629 g., 0.01 1 mole) in 10 ml of m-cresol was added, after which the solution was heated to reflux; during 2 hours of reflux 0.25 ml. of water was collected. After cooling, the solution was made up to ml. with added benzene, and it was divided into two 40-ml. portions.

The first 40-ml. fraction was added to 250 ml. of methanol and then stirred for 1 hour. This solid material was isolated by centrifuging and dried in a vacuum oven at 80C. for 36 hours, yielding a yellow solid (A), 1.87 g.

The second 40-ml. fraction was evaporated on a rotary flash evaporator and the residue was dried in a vacuum oven at 80C., yielding a yellow solid (B), 2.306 g. (104%). Sample B softened at C., was nearly completely molten at 200-300C., darkened in 10 minutes at 230C, was soluble in hot m-cresol, slightly soluble in hot DMAC, and insoluble in acetone.

Analysis: Calcd. for C l-1 N C, 70.42; H, 3.41; N, 6.32; O, 19.85. Found: C, 70.99; H, 3.79; N, 6.47; O,

A sample of BTAA-3B was postheated in nitrogen at 300C. for 24 hours, and its TGA in nitrogen, at l0C./minute, showed an inflection point at 360C.

e. Preparation of Aliphatic Nitrile-terminated Oligomeric Polyimide (BTBN-l Reaction of BTCA, ODA and 4-Aminobenzyl Cyanide (BN) (2:1:2).

In the m-cresolzbenzene azeotropic apparatus was placed a solution of BTCA (3.222 g., 0.01 mole) in 25 ml. m-cresol and ml. of benzene. The mixture was warmed to approximately 50C. and a solution of ODA (1.001 g., 0.005 mole) in 15 ml. of m-cresol was added, giving an immediate yellow precipitate. After refluxing for 15 minutes, a solution of aminobenzyl cyanide (BN) (1.454 g., 0.011 mole) in 10 ml. of m-cresol was added. The precipitate dissolved quickly. During 1%. hours of reflux, 0.30 ml. of water was collected and a precipitate formed. Then sodium acetate (0.041 g., 0.0005 mole) was added and reflux was continued for another hour, and another 0.05 ml. of water was collected. After cooling, the solvents were removed on a rotary flash evaporator and the residue was dried in a vacuum oven at 100C., the yield was 5.170 g. 100%). Its infrared spectrum was consistent with the expected structure. Benzylcyanide-terminated oligomeric polyimide based on BTCA (BTBN-l softened at 200C., was almost completely melted by 290C. and rehardened rapidly at 300C. Also, it was soluble in hot m-cresol, slightly soluble in hot DMAC, and insoluble in acetone. A sample dried at 300C. was also submitted for analysis.

Analysis: Calcd. for C H N O :C, 71.81; H, 3.11; N, 8.11; O, 16.97. Found (B): C, 70.28; H, 3.22; N, 8.12; O, (dried at 300C.)

The TGA in nitrogen on the sample dried at 300C. showed an inflection point of 360C.

f. Preparation of Aliphatic Nitrile-Terminated Oligomeric Polyimide (BTBN-3). Reaction of BTCA, SDA- 3,3 and EN (9:822).

According to the azeotropic procedure used in (b) above, BTCA (2.1752 g., 0.00675 mole), BN (0.1982 g., 0.0015 mole) and SBA-3,3 (1.4898 g., 0.0060 mole) were allowed to react. There was obtained 3.27 g. (91%) of a light-yellow solid (BTBN-3). The yield, corrected for approximately 1% retained m-cresol, was 89%.

The oligomer melted at 25026-C., and rehardened at 290C. It was soluble in m-cresol, DMAC and hot sulfonlane but insoluble in dioxane.

A small portion, vacuum-dried at 200C. for 4 hours showed a 1% loss of retained m-cresol, which was confirmed in its TGA in nitrogen which also showed an inflection point in the 500C. region.

The above procedure was repeated except that the quantities used were such as to yield a larger amount of product: BTCA, 21.750 g., 0.0675 mole; SDA-3,3, 14.899 g., 0.060 mole; BN, 1.982 g., 0.0150 mole. The BTBN-3 obtained from this reaction amounted to 34.8 g. (96%).

Analysis: Calcd. for C H N O ,S C, 65.94; H, 2.72; N, 5.80; O, 20.22; S, 5.32. Found: C, 65.18; H, 2.65; N, 5.71; O, S,

g. Preparation of Aliphatic Nitrile-Terminated Oligomeric Polyimide (BTBN-4). Reaction of BTCA, DAPB-3,3 and EN (9:8:2).

According to the procedure used in (c) above to prepare BTAN-4, BTCA (2.1753 g., 0.00675 mole), BN (0.1982 g., 0.0015 mole) and DAPB-3,3 (1.7540 g., 0.0060 mole) were allowed to react to afford, after vacuum-drying at C., BTBN-4, 3.8 g. (97%) as a light-yellow solid. BTBN-4 was soluble in m-cresol, DMAC, sulfolane and dioxane. It was partially soluble in hot chloroform and hot methylene chloride, and was insoluble in acetonitrile.

On a Fisher-Johns melting point apparatus, BTBN-4 softened at 135C., melted at 196215C., thickened above 235C. and remelted at 255C. It did not reharden when held for one-half hour at 300C. A sample of BTBN-4, vacuum-dried at 200C., was submitted for analysis.

Analysis: Calcd. for C H N O C, 72.20; H, 3.20; N, 5.49; O, 19.11. Found: C, 72.21; H, 3.15; N, 5.44; O,

h. Preparation of Styrene-Terminated Oligomeric Polyimide (BTAS-l Reaction of BTCA, ODA and m- Aminostyrene (AS) (2:1:2).

1n the m-cresol:benzene azeotropic apparatus was placed a solution of BTCA (3.222 g., 0.01 mole) in 25 ml. of m-cresol and 10 ml. of benzene. After warming to approximately 70C., a solution of ODA (1.001 g., 0.005 mole) in 15 ml. of m-cresol containing 2 mg. of t-butyl catechol was added, forming an immediate yellow precipitate. After heating for 15 minutes, a solution of m-aminostyrene (AS) (1.192 g., 0.01 mole, Sapon Laboratories) in 10 ml. of m-cresol was added and the solution was heated to reflux, forming a homogeneous solution. After 1 hour of reflux, a precipitate began to form. After 2 hours of reflux, during which 0.25 ml. of water was collected, the reaction mixture was cooled and poured into 250 ml. of methanol. After stirring for several hours, the solid material was filtered off, washed with methanol and vacuum-dried at 40C. for 18 hours. The sample still had a distinct odor of mcresol. A small portion was removed and vacuum-dried at 200C. for 24 hours to give fraction A whose infrared spectrum was recorded. The remainder of the material was finely divided and stirred with 50 ml. of ether, and dried at 40C. to afford 4.0402 g. of a yellow powder, fraction B. The infrared spectrum of sample A was substantially the same as that of sample B.

Sample A softened at 220C.; was partially molten at 250C. when pressure was applied; was almost completely molten at 300C. when pressure was applied; and rehardened (cured) to a granular solid after 25 minutes at 300C. Sample A was slightly soluble in hot m-cresol.

Sample B softened at 70C.; was nearly completely molten at 225C. with applied pressure; and hardened (cured) to a granular solid at 250C. Sample B was soluble in hot m-cresol, and virtually insoluble in sulfolane, DMAC and toluene.

Analysis: Calcd. for C H N O C, 73.66; H, 3.39; N, 5.54; O, 17.41. For A Found: C, 73.21; H, 3.67; N, 5.79; O,

A portion of sample B was postheated in nitrogen at 300C. for 24 hours, and a TGA performed in nitrogen at 10C./minute, showed an inflection point of 410C. i. Preparation of Styrene-Terminated Oligomeric Polyimide (BTAS-3). Reaction of BTCA, DAPB-3,3 and AS (8:7:2).

In the m-cresolzbenzene azeotropic apparatus fitted with provisions for a nitrogen sweep, was placed a warm solution of BTCA (1.2889 g., 0.004 mole) in 25 ml. of m-cresol and 10 ml. of benzene containing 1-2 mg. of t-butyl catechol. Then a solution of AS (1.1 192 g., 0.01 mole) in 5 ml. of m-cresol was added and the solution was then stirred and heated at approximately 70C. for 15 minutes. Then a solution of DAPB-3,3 (1.023 g., 0.0035 mole) in ml. of m-cresol was added and the solution heated to reflux which was maintained for 4 hours, during which time, approximately 1.5 ml. of water was collected. Then the benzene was distilled off. After cooling to ambient temperature, the slightly hazy solution was added dropwise to 150 ml. of methanol. The solid was filtered off and washed three times in 30 ml. of boiling methanol, which contained a trace of t-butyl catechol, for minutes each time, then it was given a final wash with inhibitor-free boiling methanol. The yellow solid was filtered and vacuum-dried at room temperature for two days to give BTAS-3, 1.782 g. (78%) as a yellow solid. Its TGA in nitrogen at l0C./minute showed the retention of m-cresol solvent.

On a Fisher-Johns melting point block, it melted at l90-195C., hardened at 205C, resoftened and remelted at 210233C., and rehardened at 268C. Its DTA at C./minute showed a melting endotherm at 183C. BTAS-3 was soluble in dioxane, m-cresol, DMAC and sulfolane; it swelled in tetrahydrofuran, styrene, divinylbenzene and toluene, and was insoluble in methyl ethyl ketone.

A portion of BTAS-3 was vacuum dried at 200C. for 36 hours and analyzed.

Analysis: Calcd. for C H -N O C, 72.99; H, 3.22; N, 4.90; O, 18.89. Found: C, 73.55; H, 3.31; N, 5.03; O,

j. This oligomer (BTAS-4) is prepared in Example 3 above.

k. Preparation of Styrene-Terminated Oligomeric Polyimide (BTAS-lOR). Reaction of BTCA, 4,4- Methylenedianiline (MDA-4,4) and AS (9:8:2).

In the m-cresolzbenzene azeotropic apparatus equipped with a nitrogen inlet and outlet, there g. placed BTCA (21.7505 g., 0.0675 mole) in 80 ml. of m-cresol and 40 ml. of benzene. The temperature of the mixture was raised to approximately 70C. as nitrogen was passed through the apparatus, and a solution of m-aminostyrene (AS) (1.7874 g., 0.015 mole) in 40 ml. of m-cresol containing 0.1 g. of t-butyl catechol was added over 15 minutes, and the solution was stirred for an additional 15 minutes. Then a solution of 4,4- methylenedianiline (MDA-4,4) (11.8956 g., 0.060 mole) in 55 ml. of m-cresol was added and the solution was brought to reflux. After refluxing for 3 hours, during which 2.35 ml. of water was collected, a copious yellow precipitate was present. Then, the benzene was distilled off and the reaction solution was added dropwise to methanol. The precipitated oligomer was digested three times in hot methanol containing approximately 0.1 g. oft-butyl catechol and then vacuum-dried at ambient temperature for 63 hours to afford BTAS- 10R, 32.565 g. (98.7%), whose infrared spectrum was consistent with that expected for the compound.

A 2.25 g. sample of BTAS-lOR was washed once with methanol to remove the inhibitor to afford 2.190 g. of inhibitonfree BTAS-lO, whose DTA in air showed a slight endotherm at 150C, followed by an exotherm at 175C.

Analysis: Calcd. for C H N O C, 74.52; H,

3.39; N, 5.73; O, 16.36 Found: C, 73.38; H, 3.52; N, 5.84; O, 16.59. 1. Preparation of Styrene-Terminated Oligomeric Polyimide (BTAS-l 1 Reaction of BTCA, 1,3-Di(4-Aminophenoxy)benzene (DAPB-3,4) and AS (9:8:2).

By the procedure used in the preparation of (k) above, there was reacted BTCA (1.8126 g., 0.00563 mole) in 25 ml of m-cresol and 20 ml of benzene, a solution of AS (0.14909) g., 0.00125 mole) in 10 ml. of m-cresol containing 0.1 g. t-butyl catechol. and a solution of 1,3-di(4-aminophenoxy)benzene (DAPB-3,4) (1.4617 g., 0.005 mole) in 20 m1. of m-cresol. After refluxing for 5 hours, there was obtained 0.35 ml. of water and solution had not occurred. Then the benzene was distilled off and the reaction mixture was slowly poured into methanol to precipitate the oligomer. The oligomer was digested thred times in hot methanol containing 0.1 g. t-butyl catechol and vacuum-dried at 40C. to give 3.4882 g. (96.8%) of BTAS-ll as a yellow powder. A small portion of BTAS-l l was digested again in hot methanol to remove the inhibitor for use in testing. Its infrared spectrum was consistent with that expected for the compound.

The TGA in air showed the retention of about 3% mcresol and an inflection point in the 500C. region.

Analysis: Calcd. for C H N O C, 72.96; H,

3.21; N, 4.89; O, 18.94. Found: C, 72.22; H, 3.11; N, 4.69; O m. Preparation of Styrene-Terminated Oligomeric Polyimide (BTAS-l Reaction of l,4,5,8-Naphthalenetetracarboxylic Acid Dianhydride (NTCA), DAPB-3,3 and AS (9:8:2).

According to the precedure given for (1) above, there was allowed to react 1,4,5,8-naphthalenetetracarboxylic acid dianhydride (NTCA) (2.8369 g., 0.01125 mole), DAPB-3,3(2.9233 g., 0.01 mole) and AS (0.2979 g., 0.0025 mole). There was obtained NTAS-l as a tan powder which partially melted, with darkening at 220260C., rehardened at 265C., and then did not change up to 300C. When a sample was placed on a Fisher-Johns apparatus at approximately 220C., it became completely molten by 260C. and rehardened at about 265C.

NTAS-l was soluble in DMAC, m-crosol, sulfolane and concentrated sulfuric acid, and swelled in hot dioxane. Its infrared spectrum was consistent with that expected for the compound.

Analysis: Calcd. for C H N O C, 73.61; H, 3.15; N, 5.40; O, 17.83. Found: C, 73.74; H, 3.50; N, 5.83; O,

n. Preparation of Styrene-Terminated Oligomeric Polyimide (PMAS-l Reaction of Pyromellitic Anhydride (PMA), DAPB-3,3 and AS (9:8:2).

According to the procedure given for (1) above, there was allowed to react pyromellitic anhydride (PMA) (2.4538 g., 0.01125 mole), DAPB-3,3 (2.9233 g., 0.01 mole) and AS (0.2979 g., 0.0025 mole). Complete solution did not occur during the reaction period. There was obtained PMAS-l which melted at 150210C., rehardened at 240C., and resoftened at 275C, and rehardened after 20 minutes at 300C. PMAS-l swelled in m-cresol, and was insoluble in concentrated sulfuric acid, hot DMAC, sulfolane and dioxane. lts infrared spectrum was consistent with that expected for the compound. Its DTA in air and its TGA 35 in air showed solvent retention and an inflection point in the 500C. region.

Analysis: Calcd. for C H N O C, 71.22; H, 3.06; N, 5.98; O, 19.74. Found: C, 71.22; H, 3.22; N, 6.17; O, i

B. Dipolar Cycloaddition Reactions In Examples 1 156, three procedures, A to C inclusive, were used to prepare cycloaddition reaction products of some dipolarophilic-terminated oligomeric polyimides prepared in (a) to (n) of Part A of this Example with the two dipoles l,4-benzenedinitrile oxide (BDNO) and l,4-benzenedi(phenylnitrilimine (BDNI). However, basically, the three procedures are equivalent. Minor modifications were introduced to accommodate the particular systems used. For example, in some cases a highly soluble oligomer required less solvent in which to perform the reaction.

Procedure A:

The acceptor was first dissolved in 18 ml. of mcresol, by warming if necessary. The solid dipole was added and the mixture was stirred at ambient temperature until solution was effected. The solution was then placed in an air oven at 70-80C. for 5 to 8 days, after which the temperature was raised to 200C. for 1 day. Finally, the samples were vacuum-dried at 200C. for 1 day, and the weight recorded. Small samples were dried in an air oven at 200C., 240C. or 300C. for 24 hours and the temperature at which they were cured designated by the suffix, H200, H240 and H300 after the polymer number.

Procedure B:

The acceptor was first dissolved in 5-l0 ml. of mcresol, by warming if necessary. Then solid dipole was added and the mixture was stirred at ambient temperature until solution occurred, after which the solution was then placed in an air oven at 100C for 24 hours, and then at 200C. for 48 hours. The residues were then vaccum-dried at 200C. for 24 hours and the weights recorded. Small samples were dried in an air oven at 300C. for 24 hours and are designated as Procedure C:

This procedure is a modification of Procedure B in that, after mixing, the samples were allowed to stand at ambient temperature for 48 hours and then were heated to 200C. over an 8-hour period. After drying in an air oven at 200C. for 48 hours, the residues were vacuum-dried at 200C. for 24 hours and the weights were recorded.

BDNI and BDNO were prepared as follows:

Synthesis of 1,4-Benzenedi(phenylnitrilimine)p- C H (C=NNC H BDNI 1. Intermediate Terephthaloylphenylhydrazide Chloride,

A mixture of 5.8 g. (0.016 mole) of terephthaloylphenylhydrazide, (mp. 265C), 7.5 g. (0.036 mole) phosphorous pentachloride in 60 ml. anhydrous ether was heated under reflux for 24 hours during which time the mixture remained heterogeneous. Then 20 g. phenol (0.212 mole) in 20 ml. ether was added to the mixture, followed by the slow addition of 30 ml. (0.74 mole) of methanol and allowed to cool to room temperature. The yellow crystals which formed were separated by the filtration. The filtrate was concentrated at 50C. until more crystals appeared; these were isolated by filtration. The crude product was recrystallized from benzene, yielding, 2.14 g. (35.0%); m.p., 216217C. Its infrared spectrum showed the C=N absorption at 6.3a; the amide peak,

-CNH- by filtration, washed with distilled water and dried in a vacuum oven at 30C.; yield of brown powder, 0.152 g. m.p. 180185C. (with resinification).

BDNI is used within 72 hours after its preparation.

Synthesis of 1,4-Benzenedinitrile Oxide BDNO 1. Intermediate Terephthaldehyde Dioxime, p- C H.,(Cl-l=NOl-l) Into a 2-liter Erlenmeyer flask were place 45 g. (0.66 mole of hydroxylamine HCl dissolved in 237 ml. of water and 26.4 g. (0.66 mole) of sodium hydroxide dissolved in ml. ,of water; this-mixture was thoroughly agitated. Then 40.2 g. (0.3 mole) of terephthaldehyde, dissolved in 300 ml. of ethanol was added to the mixture,-which remained clear for a few seconds, then a large amount of white precipitate formed. The mixture was brought to reflux on a steam bath, then 200 ml. of 95% ethanol was added to dissolve the precipitate, and reflux was continued for 30,.minutes, after which the mixture wascooled in an ice water bath, and the white crystals which precipitated were recovered by filtration. The crude dioxime was recrystallized from a 55% ethanol 45% water solution. The yield of recrystallized product was 95% based on terephthaldehyde; m.p. 220222C. Its'infrared spectrum showed bands for C=N at 6.14 and 6.6a; for -Ol-l absorption at 3.3,

Into a suspension of 2.3 g. terephthaldehyde dioxime (A above) in 45 ml. CCl, was passed slowly with stirring a stream of C1 gas for a period of 1.5 hours. The i temperature of the reaction mixture was held below 0C. by means of an ice-salt cooling bath, then the mixture was allowed to remain at room temperature overnight. The suspended solids were recovered from CCl;

by filtration and were recrystallized twice from 10% ethanol-90% chloroform.v White crystals were obtained, m.p. l84186C.

.37 3. Synthesis of 1,4-Benzenedinitri1e Oxide (BDNO) A solutionof 16.7 g. (0.0716 mole) of terephthalhydroxamoyl chloride in 270 ml. of diethyl ether was added over a period of 15 minutes to a well stirred solution of 21 g. of triethylamine (0.21 mole) in 760 ml. of 5 diethyl ether; the reaction was maintained at 02C. with a salt-ice cooling bath. A voluminous precipitate was formed and after stirring for minutes, 60 m1. of ice-water was added to the reaction mixture and stirring continued for an additional 30 minutes. Then the 10 precipitate was recovered by filtration, washed thor- Table VI Data on Dipolar Cycloaddition Reactions of Various Oligomeric Polyimides Molar TGA Example Pro- Oligomer Dipole Ratio 71 Cured Break Inflection No. cedure (O1) Grams (Di) Grams 0|:Di Yield at C. Atmosphere C. Point C.

1 1 A BTAS-l 0.505 BDNO 0.0190 1:1 100 200 nitrogen 320 (320) (h) 240 nitrogen 360 (520) 12 A BTAS-l 0.505 BDNl 0.105 1:1 107 240 nitrogen 300 (350) (h) 300 nitrogen 340 (510) 13 B BTAS-3 0.4478 BDNO 0.016 1:1 100 200 air 270 560 (i) 300 air 380 580 14 B BTAS-4 0.4882 BDNO 0.0640 1 :4 1 10 200 nitrogen 380 510 (j) 200 air 380 490 15 B BTAS-4 0.4882 BDNO 0.0160 1:1 108 200 nitrogen 425 530 (j) 200 air 400 530 16 B BTAS-4 0.4882 BDNO 0.0120 4:3 104 200 nitrogen 435 5 30 (j) 200 air 375 515 17 C BTAS-4 0.4882 BDNO 0.0160 1:1 99.5 200 air 300 550 (j) 300 air 375 540 18 B BTAS-4 0.4882 BDN1 0.0310 1: 1 102 200 air 250 550 (j) 300 air 400 550 19 C BTAS-4 0.4882 BDNI 0.0310 1:1 1 12 200 air 300 530 (j) 300 air 360 520 20 B BTAS-4 0.4882 BDNl 0.0232 4:3 104 200 air 300 540 (j) 300 air 400 540 21 B BTAS-10 0.440 BDNO 0.0160 1: 1 92.98 200 air 390 560 (k). 22 B BTAS-IO 0.440 BDNO 0.0120 4:3 101.26 200 air 380 550 (k) 23 B BTAS-lO 0.440 BDNI 0.310 1:1 101.57 200 air 390 530 (k) 24 B BTAS-IO 0.220 BDN1 0.0116 4.3 108.18 200 air 310 550 (k) 25 B BTAS-l 1 0.2576 BDNO 0.008 1:1 104 200 air 330 555 (1) 300 air 390 5 80 26 B BTAS-l 1 0.2576 BDNO 0.006 4:3 103 200 air 330 555 (l) 300 air 410 585 27 B NTAS-l 0.4666 BDNO 0.016 1:1 1 10 200 air 350 510 (m) 300 air 350 525 28 B NTAS-l 0.4666 BDNO 0.012 4:3 109 200 air 350 505 (m) 300 air 400 525 29 B PMAS-l 0.4216 BDNO 0.016 1:1 98 200 air 300 515 (n) 300 air 380 530 30 B PMAS-l 0.4216 BDNO 0.016 4:3 99 200 air 310 570 (n) 300 air 310 570 31 A BTAN-2 0.5045 BDNO 0.080 1: l 98 200 nitrogen 200 430 (a) 300 nitrogen 300 520 32 A BTAN-Z 0.5045 BDNO 0.320 1:4 100 200 nitrogen 200 350 (a) 300 nitrogen 350 550 33 A BTAN-2 0.5045 BDNl 0.105 1:1 107 240 nitrogen 250 400 "(11) 300 nitrogen 330 525 34 A BTAN-2 0.5045 BDNl 0.620 1 :4 103 240 nitrogen 250 3 30 (a) 300 nitrogen 340 530 35v B BTAN-3 "0.2399 BDNO 0.008 1:1 103 200 air 300 520 (b) 300 air 370 560 36 B BTAN-3 0.2399 BDNO 0.0320 1:4 109 200 air 300 560 (b) 300 air 360 550 37 B BTAN-3 0.2399 BDNl 0.0155 1:1 102 200 air 320 600 (b) 300 air 360 575 38 B BTAN-3 0.2399 BDNI 0.0620 1:4 106 200 air 320 585 (b) 1 i 300 air 360 570 39 B BTAN-4 0.254 BDNO 0.008 1:1 97.06 300 air 430 560 40 B BTAN-4 0.254 BDNO 0.032 1:4 1 1 1.09 200 air 360 580 (c) 41 B BTAN-4 0.254 BDNI 0.0155 1:1 100.15 200 air 390 545 (c) 42 B BTAN-4 0.254 BDNI 0.062 1 :4 95.41 200 air 400 550 (c) 43 A BTBN-l 0.5185 BDNO 0.08 1: 1 200 nitrogen 530 (c 300 nitrogen 350 540 44 A BTBN-l 0.5185 BDNO 0.320 1:4 100 :200 nitrogen 200 530 (c) 300 nitrogen 350 560 45 A BTBN-l 0.5185 BDNl 0.155 nitrogen 280 550 1:1 107 240 300 g I nitrogen 1 340 550 

1. A POLYMERIC CHAIN-EXTENDING PROCESS COMPRISING HEATING A POLYIMIDE SAID POLYIMIDE OF THE FORMULA:
 2. The process of claim 1 wherein R is
 3. The process of claim 1 wherein R is -CH2- and n is at least
 4. 4. A cross-linked polymer prepared by the polymerization process of claim
 1. 5. A cross-linked polymer prepared by the polymerization process of claim
 2. 6. A cross-linked polymer prepared by the polymerization process of claim
 3. 7. The process of claim 1 wherein the polyimide is copolymerized with a bis-maleimide of the formula:
 8. A cross-linked polymer prepared by the polymerization process of claim
 7. 9. The process of claim 1 wherein n is within the range of about 4 to
 20. 10. The polymerized product of:
 11. The polymerized product of:
 12. The process of claim 1 wherein the polyimide is heated in the presence of a catalytic amount of a free-radical initiator.
 13. A cross-linked polymer prepared by the polymerization process of claim
 12. 